U.S. Pat. No. 5,322,435 A discloses a bracket which has a slide for closing its slot, which can be displaced in lateral guiding slots, which are provided in the occlusal wall as well as in the gingival wall of the bracket. In order to hold the slide in its closed position as well as in its open position, a bore open to the slide is provided in one of the walls of the bracket, in which either a helical spring, which presses against the underside of the slide, or a cylindrical bolt made of elastomeric synthetic material is situated, which protrudes over the opening of the bore and presses against the underside of the slide. Two recesses are provided on the underside of the slide. The spring respectively the bolt with its end protruding from the bore meshes into one of the recesses when the slide is in open position. The spring respectively the bolt with its end protruding from the bore meshes into the other recess when the slide is in closed position. A protrusion separating both recesses must pass the helical spring respectively the bolt, when the slide should be displaced between its open position and its closed position. Overcoming the spring load is a tricky operation, because the slide is displaced at right angle to the direction in which the spring must be pushed back into the bore. Moreover, the slide can get caught in the spring and the spring may be damaged. The elastomeric synthetic bolt cannot be pushed back into the bore, since the synthetic material as a solid matter is not compressible. The slide must be twisted instead, to move it past the synthetic bolt. Consequently, the slide must be accordingly thin, to maintain within practical limits the force which must be applied upon displacement. With the small sizes which brackets have typically, the known bracket is difficult to realize.
A self-ligating bracket is disclosed in U.S. Pat. No. 5,613,850, in which the slide is combined with a U-shaped spring, which surrounds the slide. One or both branches of the spring is provided with a protrusion via an embossing process, so that it snaps in a recess of a bracket wing in closed position with its protrusion. Pressing down this branch enables to move the spring out of its snap-in position and to push the slide out of its closed position. The slide is not held in open position, so that it cannot be lost, which is uncomfortable in the mouth, because the slide could be swallowed.
A self-ligating bracket is disclosed in EP 1 679 048 A2, whose slide is maintained through a spring, which is inserted in a hole of the bracket body and engages in a continuous hole of the slide by means of a protruding, twice angled branch. The spring can be pushed out of the hole and the slide removed from the bracket. The spring is not able to hold the slide in open position. A further shortcoming is that food remains may build up in the hole of the slide and under the slide, which cannot be eliminated even by brushing one's teeth or repeated mouth washing.
A self-ligating bracket is moreover disclosed in EP 1 679 048 A2, whose slide has a long hole, through which a safety pin engages, which is anchored in a bore in the bracket, once the slide has been inserted in the bracket. The clearance exhibited by the safety pin in the long hole limits the path over which the slide can be displaced in the bracket between closed position and open position. Once the safety pin has been inserted the slide cannot be removed any longer. The safety pin is not able to hold the slide in closed position and in open position. Only friction can block the slide to a certain extent, which does not enable reliably to hold the slide in closed position or in open position.
Document DE 10 2006 053 215 A1 discloses a self-ligating bracket with a slide, which co-operates with a leaf spring arranged in the gingival wall of the bracket, which can be swung out sideways upon displacement of the slide. This bracket has the advantage that the leaf spring does not press against the underside of the slide and that the leaf spring can maintain the slide in its closed position as well as in its open position on the bracket body. If the bracket and its slide are however produced out of ceramic material by powder metallurgy, for example through a CIM process (Ceramic Injection Molding), it is then difficult to respect the strict dimensional tolerances required for such a bracket.
The object of the present invention is to provide a self-ligating bracket for orthodontics, in which the slot of the bracket can be closed by a slide, which even needs no particular elastic properties, can be formed mechanically stable, is maintained captive in closed position as well as in open position, is easy to open and to close, confers a pleasant aspect to the bracket and offers little opportunity for the build up of food remains which are difficult to remove. Moreover, the invention should be suitable for the production of ceramic brackets.